Blurring can appear in an image when a subject moves or the photographer causes camera-shake at the time of image capture, and a method of using a Wiener filter, an RL method, and the like are publicly known as algorithms for removing this kind of blurring. Also, “blur direction”, which is the direction in which the subject moves, the direction of camera-shake, or the like is often a parameter in blur correction for removing this kind of blurring (see Patent Literature 1: JP 2007-295427A and 2: JP 2006-180429A). The blur direction parameter can be estimated based on a detected value of a camera-shake correction mechanism such as a gyro sensor that is mounted in the camera (e.g., Patent Literature 1), but even without that information, it is possible to estimate the blur direction parameter based on the image in which blurring appears. For example, in Patent Literature 2, the blur direction of the subject is estimated based on the movement of feature points in two images captured in succession.
As mentioned above, beginning with Patent Literature 2, various algorithms for estimating blur direction based on the blurred image itself have been proposed in the prior technology, but these algorithms are effective only under specific conditions (e.g., when the blurring is linear, or when the blurring occurs at a fixed speed). Accordingly, an algorithm that is effective under specific conditions is not effective for all images, and it is difficult to obtain an image from which blurring has been removed to the user's satisfaction.